How Many Sisters?

There is no better time for gazing at the heavens than in mid winter. Directly overhead, about 9 pm, are three bright star clusters and constellations: Orion, the Hyades, and the Pleiades. Part of the show are the super stars Sirius and Betelgeuse.

Orion the Hunter holds up his shield, warding off Taurus the Bull (containing the Hyades star cluster), who in turn defends the Seven Sisters of the Pleiades. Following close on Orion’s heels is Canis Major (Great Dog), whose bright nose is Sirius, the brightest star in our sky. Inset into Orion’s shoulder is giant red Betelgeuse. Each one of these objects is notable on its own. Together they are a light show that surpasses Las Vegas.

The Hyades is a group of a half dozen stars shaped like a V. It’s a true cluster—in that all of its stars are related. (In contrast, the stars of the Big Dipper, although they appear to be grouped, are disconnected and at vast distances from one another. They just appear to be aligned, from our vantage point.)

Orion contains some of the brightest stars in the northern hemisphere. His belt is three vivid blue stars that grab your eye. The shoulder star Betelgeuse is ancient; it's over 50,000 times brighter than our Sun and 500 times its size. If it were put where our Sun is, it would engulf the Earth and Mars.

Hanging from Orion’s dazzling belt is a sword of three stars. But the middle one is not a star; it’s the Orion Nebula—an immense cloud of interstellar gas, which is the blown-out leftovers of an ancient supernova. Today the clumps of gas are coalescing into new stars It’s a hot and active star nursery.

Yipping at Orion is Canis Major. The dog’s nose, Sirius, is the brightest star in our sky—24 times brighter than our Sun. Although Sirius appears to be an intense point of light to the naked eye, it is really a double (binary) star. Half the stars in our Milky Way are binary stars, but most can’t be separated with the naked eye. The Egyptians cast Sirius as one of their key stars. Its appearance each year heralded the flooding of the Nile.

Finally there’s the Pleiades. Pretty little Pleiades. It has a mystical, magical quality to it. It resembles a miniature teapot; sort of like a tiny Dipper. Its alternative name—the Seven Sisters—is Subaru in Japanese. Take a look at that car’s logo and get an idea of how the cluster appears.

When I look at the Pleiades I see six stars, not seven. So where does the name Seven Sisters come from? Greek mythology describes the seven daughters of Atlas being turned into stars by Zeus. So Pleiades got its label.

Some people have claimed seeing as many as 16 stars in the Pleiades cluster. I suspect it’s a little like a macho game of “Mine’s bigger than yours.” He who sees more stars is the winner. But there’s a way to beat all the braggers. Take up a pair of binoculars and you can see dozens of stars in Pleiades. Big telescopes register as many as 3000 young stars in the cluster—all a brilliant blue.

I can’t stand outside very long on mid winter nights, looking up at these stellar favorites of mine. The cold sinks too deep into my old bones. But I’m always stopped dead in my tracks by the sight of them, as I cross the yard. It’s delight that never tires.